Plasma disappearance curves of radiolabeled bilirubin, sulfobromophthalein, indocyanine green and bile acids are obtained in normal volunteers, patients with hepatic disease and experimental animals. Curves are analyzed by computer to calculate anion clearance and, in the case of bilirubin, daily bilirubin turnover. Data are further analyzed in terms of compartmental models to estimate hepatic uptake and conjugation rates, storage capacity, liver: plasma concentration gradients and other parameters of the hepatic organic anion transport mechanism which are of interest both for physiologic studies and in the diagnostic classification of hepatic dysfunction. Studies of the hepatic metabolism of conjugated bilirubin have been facilitated by the isolation of pure radiolabeled conjugates of bilirubin. An appreciable affinity of conjugated bilirubin for intrahepatic binding proteins, such as ligandin, and the existence of a significant intrahepatic storage pool for conjugated bilirubin have been demonstrated. These two observations make a re-examination of current concepts of the nature of the hepatic excretion of conjugated bilirubin necessary. BIBLIOGRAPHIC REFERENCE: Wolkoff, A.W., Scharschmidt, B.F., Plotz, P.H., and Berk, P.D.: Purification of conjugated bilirubin: A new approach utilizing albumin-agarose gel affinity chromatography. Proc. Soc. Exper. Biol. Med. 152: 20-23, 1976.